I forget this part of IPv6 class (I've literally gone to several IPv6 classes throughout the years but then end up forgetting details because I've yet to use it

I forget this part of IPv6 class (I've literally gone to several IPv6 classes throughout the years but then end up forgetting details because I've yet to use it in production), but since the IPv6 space is so large, it's trivial to put an IPv4 address into it, and so they make NAT 6to4 type gateways that map the IPv4 internet into a block on the IPv6 network.